In a conventional air conditioner for a vehicle, a receiver-type refrigerant cycle is provided. In the receiver-type refrigerant cycle, refrigerant flowing out of a radiator is separated in a receiver into gas refrigerant and liquid refrigerant, and the separated liquid refrigerant is stored in the receiver as a surplus refrigerant of the refrigerant cycle. In the receiver-type refrigerant cycle, a thermal expansion valve is used as a decompression device, and a refrigerant flow amount is automatically controlled such that a superheating degree of refrigerant at a refrigerant outlet of an evaporator is maintained at a predetermined value.
The thermal expansion valve is provided with a block-shaped body portion forming an outer shell. The block-shaped body portion has therein a refrigerant passage through which high-pressure refrigerant flows, a throttle passage for decompressing and expanding the high-pressure refrigerant, and a refrigerant passage through which the refrigerant flowing out of the evaporator flows. Furthermore, a temperature sensing rod, a valve body and the like are disposed in the body portion of the thermal expansion valve. Furthermore, an element is disposed outside of the body portion to be displaced in accordance with temperature and pressure of the refrigerant flowing out of a refrigerant outlet of the evaporator. Generally, the thermal expansion valve is called as a box-type expansion valve.
In contrast, in an accumulator-type refrigerant cycle, an accumulator is disposed between a refrigerant outlet side of an evaporator and a refrigerant suction side of a compressor, to separate the refrigerant into gas refrigerant and liquid refrigerant and to store the separated liquid refrigerant. In the accumulator-type refrigerant cycle, a supercooling degree of refrigerant at a refrigerant outlet of a condenser is maintained to a suitable range (e.g., 7-15° C.), thereby increasing a cycle efficiency.
For example, in Patent document 1 (JP Patent No. 3757784B2 corresponding to US 2001/0027657), a refrigerant flow amount is controlled while the supercooling degree of refrigerant at a refrigerant outlet side of a condenser is maintained in a suitable range, thereby increasing cycle operation efficiency even when cycle operation condition is changed in a wide range.
In the Patent document 1, a decompression device is provided with a variable throttle located at a refrigerant upstream side, and a fixed throttle located at a refrigerant downstream side. In the fixed throttle with a nozzle shape, a variation in the refrigerant flow amount is large when the dryness x of the refrigerant is small (for example, 0<x<0.1), and thereby a flow amount adjustment gain is large. In view of the above point, in the decompression device of the Patent document 1, the supercooling refrigerant at the refrigerant outlet side of the condenser is decompressed by the variable throttle at the refrigerant upstream side such that the refrigerant decompressed by the variable throttle is changed in the small dryness range, and the gas-liquid two-phase refrigerant flows into the fixed throttle to be decompressed again.
Thus, the fixed throttle can perform a refrigerant flow amount adjustment in a refrigerant state with a large adjustment gain. Accordingly, even when the operation condition of the refrigerant cycle is changed, the refrigerant flow amount can be adjusted in a wide range by the small variation range of the supercooling degree. Therefore, the supercooling degree of the refrigerant at the refrigerant outlet of the condenser can be maintained in a suitable range in which the cycle operation efficiency can be increased, and thereby the cycle operation can be performed with a high efficiency.
However, in the decompression device of the Patent document 1, because the variable throttle and the fixed throttle are arranged on the same straight line, the dimension of a refrigerant tube in the axial direction becomes larger, and it is difficult for the refrigerant tube to be disposed in the block-shaped body portion.
When the decompression device of the Patent document 1 is used in the accumulator-type refrigerant cycle instead of the box-shaped expansion valve that is generally known, the decompression device is required to be mounted into a refrigerant pipe or to be connected between refrigerant pipes. In this case, it is necessary to greatly change the specifications of other components (e.g., air conditioning unit (HVAC) or joint) of the air conditioner. Therefore, a production cost increases due to a design change or/and production facility change or the like.
The present invention is made in view of the above matters, and it is an object of the present invention to provide a decompression device, which can be suitably used for an accumulator-type refrigerant cycle without greatly changing the specification of other components generally used in a refrigerant cycle, while improving the cycle operation efficiency.
It is another object of the present invention to provide a decompression device which can be easily adapted to a refrigerant cycle while improving the cycle operation efficiency.
According to an aspect of the present invention, a decompression device for decompressing a high-pressure refrigerant of a refrigerant cycle includes a body portion having a block shape; an upstream throttle portion provided in the body portion at an upstream side of a refrigerant flow; a middle passage portion provided in the body portion at a downstream side of the upstream throttle portion such that the refrigerant having passed through the upstream throttle portion flows through the middle passage portion; and a downstream throttle portion arranged as a fixed throttle in the body portion at a downstream side of the middle passage portion such that the refrigerant having passed through the middle passage portion flows into the downstream throttle portion. In the decompression device, the upstream throttle portion is a variable throttle including an upstream throttle passage in which the refrigerant is decompressed and expanded, and a valve body having an open degree adjusting portion configured to adjust an open degree of the upstream throttle passage, and a refrigerant passage defined from the upstream throttle portion to the downstream throttle portion through the middle passage portion is provided in the body portion and is bent at least at a bent portion in which the refrigerant flow is bent in the body portion.
In the above decompression device, because the upstream throttle portion configured by a variable throttle and the downstream throttle portion configured by a fixed throttle are used, the cycle operation efficiency can be improved. Furthermore, because refrigerant passage defined from the upstream throttle portion to the downstream throttle portion through the middle passage portion is provided in the body portion and is bent at least at the bent portion in which the refrigerant flow is bent in the body portion, the size of the body portion, in which the upstream throttle portion, the downstream throttle portion and the middle passage portion are arranged, can be effectively reduced. Furthermore, the decompression device can be easily used instead of a conventional box-shaped expansion valve. Thus, it is possible for the other components of a receiver-type refrigerant cycle to be adapted to an accumulator-type refrigerant cycle, without greatly changing the specifications of the other components.
For example, the upstream throttle portion may include an upstream throttle passage in which the refrigerant is decompressed and expanded, and a valve body having an open degree adjusting portion configured to adjust an open degree of the upstream throttle passage. Furthermore, the upstream throttle portion may be configured by a variable throttle having a valve chamber in which the valve body is slidably accommodated, the valve body may be provided with a partition portion that divides the valve chamber into an inlet-side pressure chamber and a middle-side pressure chamber, the inlet-side pressure chamber may be provided to communicate with an inlet side refrigerant passage and the upstream throttle passage so that the refrigerant from the inlet side refrigerant passage flows into the upstream throttle passage through the inlet-side pressure chamber, the middle-side pressure chamber may communicate with the middle passage portion through a pressure equalization portion such that the refrigerant flows into the middle-side pressure chamber from the middle passage portion, and the valve body may be configured to cause the partition portion to be displaced in accordance with a pressure difference between the inlet-side pressure chamber and the middle-side pressure chamber, so that the open degree adjusting portion adjusts the open degree of the upstream throttle passage. Accordingly, even when the upstream throttle portion, the middle passage portion and the downstream throttle portion are not arranged on the same straight line, the upstream throttle portion can be configured as a differential pressure valve in which the throttle open degree is changed in accordance with a pressure difference between its upstream side and its downstream side.
Furthermore, the decompression device may be provided with a downstream throttle-passage forming member defining therein a downstream throttle passage in which the refrigerant is decompressed and expanded. In this case, the downstream throttle-passage forming member may be attached to the body portion to configure the downstream throttle portion. Alternatively, the body portion may directly form therein a downstream throttle passage in which the refrigerant is decompressed and expanded, thereby configuring the downstream throttle portion.
The body portion may be attached to an attachment member to be attached, the attachment member may include a protruding portion protruding to the body portion, and the body portion may have therein an insertion hole at a downstream side of the middle passage portion. In this case, the protrusion portion of the attachment member is inserted into the insertion hole of the body portion, the protrusion portion of the attachment member has therein a refrigerant passage through which the refrigerant flowing out of the middle passage portion flows in a state where the protrusion portion is inserted into the insertion hole, the refrigerant passage provided in the protrusion portion has a protrusion-side throttle passage in which the refrigerant is decompressed and expanded, and the downstream throttle portion is configured by the protrusion-side throttle passage.
A film seal member may be disposed in the valve chamber at a side of the middle-side pressure chamber of the valve body to seal the inlet-side pressure chamber and the middle-side pressure chamber from each other, and a support member may be disposed to contact an outer peripheral portion of the seal member on a side of the middle-side pressure chamber, and may be fixed to the body portion. In this case, the seal member is inserted between the body portion and the support member.
Alternatively, a circular seal member may be disposed between an inner peripheral wall surface of the body portion defining the valve chamber and an outer peripheral surface of the valve body, to be elastically deformable. In this case, the seal member seals the inlet-side pressure chamber and the middle-side pressure chamber from each other.
The valve body may be divided into a first valve portion and a second valve portion in a sliding direction. In this case, a film seal member may be disposed between the first valve portion and the second valve portion to seal the inlet-side pressure chamber and the middle-side pressure chamber from each other.
Furthermore, a spring may be disposed in the middle-side pressure chamber to apply a load to the valve body in a direction closing the upstream throttle passage. In this case, an adjustment screw may be disposed in the body portion to adjust the load due to the spring. Alternatively, a spring receiving member may be disposed in the body portion to support an end portion of the spring at a side opposite to the valve body.